Engine - Intermittent No Start

18-28



Intermittent "No Start" - Starter Inhibit Switch - Crankshaft Sensor or Main Relay - Diagnosis by Systems

MODEL: 92 MY XJS

DATE: 2/93



SUPERSEDES: TECHNICAL BULLETIN 86-120

ISSUE:

Intermittent "no start" conditions caused by high resistance in the starter inhibit switch, crankshaft position sensor or fuel injection main relay.

A new crankshaft sensor (DBC 12507) is available with an improved connector.

ACTION

Before replacing any components, question the customer to determine which condition occurs:

1. The starter does not crank.

2. The starter cranks but the engine will not start. This will occur most often when either
A. the engine is cold.
B. the engine is hot.

Analyze the stated symptoms carefully and proceed as follows:

Condition 1 - The starter does not crank

This condition is probably caused by high resistance in the starter inhibit switch. On XJS Convertible vehicles, there may also be a complaint of intermittent power top operation.





Replace the starter inhibit switch (C 33509) and adjust as per Section 44.15.18 of the XJS Repair Manual. Refer to Figure 1 for location.

Note:
DO NOT attempt to correct this condition by adjusting the original switch.



Condition 2 - The starter cranks but the engine will not start

A. If the condition occurs when the engine is cold and the tachometer needle bounces during cranking, there is an engine speed signal but no fuel injection. This is probably caused by high resistance in the fuel injection main relay.





Replace the fuel injection main relay, (AGU 1070). The main relay has a steel case with a red stripe and a red relay base. Refer to Figure 2 for location.

B. If the condition occurs when the engine is hot and the tachometer needle does NOT bounce during cranking, there is no engine speed signal and no fuel injection. This is probably caused by high resistance in the crankshaft position sensor.

Install a new crankshaft position (front) sensor, (DBC 12507). Refer to Section 18.30.12 of the XJS Repair Manual.



PARTS INFORMATION:

Part Number Description

C 33509 Starter Inhibit Switch

DBC 12507 Crankshaft Position Sensor

AGU 1070 Fuel Injection Main Relay


WARRANTY INFORMATION:

Fault:
Starter does not crank/starter inhibit switch
Fault Code:
7BQH
Repair Operation Number:
44.15.19
Time Allowance:
0.50 hrs.
Part Required:
Starter inhibit switch - C 33509

Fault:
Intermittent "no start"/fuel injection main relay
Fault Code:
7CEK
Repair Operation Number:
19.22.38
Time Allowance:
0.10 hrs.
Part Required:
Fuel injection main relay - AGU 1070

Fault:
Intermittent "no start"/crankshaft sensor
Fault Code:
7AKL
Repair Operation Number:
18.30.50
Time Allowance:
0.65 hrs.
Part Required:
Crankshaft position sensor - DBC 12507